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EXPLAIN how Pascal's Law governs the forces and pressures associated with a confined liquid
- Pascal's Law
- Pressure applied to a confined liquid is transmitted equally in all directions without the loss of pressure and acts with equal force on equal surfaces.
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EXPLAIN the relationship between linear displacement and the change in force between the input and output pistons of a closed hydraulic system
- When pressure (100 lbs.) is applied on one end, the liquid exerts the pressure equally in all directions. If the other end is moveable and the same size as the first end, it will have the same pressure applied and move the same distance up that the first end was pushed down.
- If the opposite end is larger than the input side, the amount of force is proportional to the increase in surface area.
- The distance moved is inverse the size.
- Examples
- Input size=Output size
- A - 10 - 10 sq in
- F - 100 - 100 lbs
- P - 10 - 10 lbs/sq in
- D- 1" - 1"
- Input size<Output size
- A - 10 - 100 sq in
- F - 100 - 1000 lbs
- P - 10 - 10 lbs/sq in
- D- 1" - 1/10"
- Input size=Output size
- A - 10 - 1 sq in
- F - 100 - 10 lbs
- P - 10 - 10 lbs/sq in
- D- 1" - 10"
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DESCRIBE a basic aircraft hydraulic system
- Main purpose is to multiply force.
- Consists of a power system and an number of actuating subsystems, depending on the requirements of the aircraft.
- Power system is considered to include:
- fluid supply (reservoir)
- power supply (pump)
- all other components leading up to, but not including, the selector valves.
- Selector valves considered part of actuating units.
- Most operate near 3,000 psi
- Current require 2 separate systems for operating the flight controls.
- Components:
- Reservoirstorage tank for hydraulic fluid and a overflow basin for excess fluid forced out of the system by thermal expansion, allow air bubbles to be purged, and separate foreign matter form the system.
- Pumps
- Hand pumps are manual.
- Power pumps are normally driven by the engine.
- Regulates volume delivery in accordance with system flow demands.
- Pressure Regulator/Unloader Valve
- Works in conjunction with constant displacement pump.
- Pressure regulator maintains set pressure in the system by diverting excess pump flow back to reservoir.
- Unloader valve will divert all pump flow back to the reservoir when the preset system pressure is reached.
- Check Valve
- allows one-way flow in a hydraulic system
- Accumulator
- Serves several purposes:
- Cushion or shock absorber by absorbing pressure surges in the system
- Supplements pump's output when the pump is under peak load by storing energy in form of fluid under pressure
- Filters
- ensure deliver of contaminant free hydraulic fluid
- Relief Valves
- Pressure limiting device installed to prevent pressure from building up to a point where seals might burst or damage may occur.
- Pressure Gauge
- indicates pressure in the hydraulic system.
- Pressure Switches
- indicates a hydraulic pressure drop that falls below allowable limits.
- Hydraulic Fuses
- Safety devices installed at strategic locations throughout a hydraulic system to detect ruptures, failed fittings, or other leaks or damage.
- Prevents excessive loss of fluid to permit operation of remaining subsystem.
- Selector Control Valves
- Used to direct the flow of fluid to the desired port of an actuating unit and return fluid to the reservoir.
- Actuators
- Convert fluid pressure into linear or reciprocating mechanical motion.
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